1. Field of the Invention
This invention relates to a process for repairing I/O pins formed on a multilayer circuit board and multilayer circuit board having I/O pin or pins repaired thereby, and in more particular a process for repairing I/O pins formed on a multilayer ceramic or glass ceramics circuit board and structure of the repaired I/O pin or pins formed on the multilayer ceramic or glass ceramic circuit board.
2. Description of the Prior Art
Formerly, the multilayer ceramic circuit board on which I/O pins were formed was a single chip module pin grid array. In such a multilayer ceramic circuit board, however, when an I/O pin was broken, there was no case of repairing the I/O pin.
In a recent multi chip module, when an I/O pin was broken, the I/O pin can be sometimes repaired. However, this is limited to a case where the I/O pin itself was broken. When the I/O pin was broken together with a part of a substrate, it was impossible to repair the I/O pin.
Recently, in view of an aspect of electrical characteristics, a substrate of low strength, such as a glass ceramics substrate, has been often used as a substrate for the multi chip module. As a result, when the I/O pin was broken, a part of the substrate was often broken therewith. In such a case, however, it was impossible to properly repair the I/O pin.
In the aforementioned glass ceramics substrate, the I/O pins are very thin and so are easily damaged or broken as shown in FIG. 1 through FIG. 4.
FIG. 1 shows a case where the I/O pin 51 is broken in the shaft region, and FIG. 2 shows a case where the I/O pin 51 is broken in the region where it is brazed. Also, FIG. 3 shows a case where the I/O pin 51 and an attachment pad 52 are both peeled off from a ceramic substrate 53 and broken, and FIG. 4 shows a case where the ceramic substrate 53 is broken together with the I/O pin 51.
In the prior multilayer circuit board, when an I/O pin was broken, the I/O pin could not be repaired, and the entire multilayer circuit board had to be replaced.
Therefore, for electronic devices which use multi chip module type added-value circuit boards, there is a problem of high repair costs.